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Old 10th February 2006, 09:54 PM   #1
diyAudio Member
 
Join Date: Jul 2004
Location: Columbus, OH
Default Best soundcard for optical out to my DEQ2496 -> DCX2496?

I'm working on my Orion clone dipoles and will be using a DEQ2496+DCX2496 combo. These will be in my media room which will have an HTPC. I'd like to put all my music on the computer with no compression (not going lossless; drives are dirt-cheap now) and want to put a good sound card in there to output the optical to my DEQ2496. This will also allow me to skip getting a 6-channel volume control as I'll be using the computer to adjust volume. Any recommendations on one? I've read a lot of good things about this cheap Chaintech card:

http://www.newegg.com/Product/Produc...82E16829120103

Also, if you know of a good wireless keyboard with volume control that would be great. Oh yeah, and any recommendations on good music playback software?

Thanks!
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Old 11th February 2006, 02:16 AM   #2
diyAudio Member
 
Join Date: May 2004
Location: Dallas, TX
Mazeroth,

Good to hear you are still working on your project. I hope however, that you will reconsider this idea. Doing digital volume control before your DEQ is a bad idea since Digital Volume control reduces the precision of the signal.

For example if you have 44.1Khz 16bit audio with 16'hFFFF (16 bits all 1s) representing the loudest sample cutting the volume to 1/4 of max that same sample becomes 16'h7FFF (16 bits, top 2 being 0, the rest 1).

The noise in digital electronics DEQ/DCX is pretty much constant. When the D to A convertor in the DCX converts the signal to analog, the lower voltage signal will have a larger Signal to Noise ratio than the full voltage signal would have.

This is why digital crossovers really need to be driven as hot as you can and attenuated after the crossover...

That being said, most optical cards will be fine for feeding the DEQ.

--Chris
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Old 11th February 2006, 02:22 PM   #3
AndrewT is offline AndrewT  Scotland
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Join Date: Jul 2004
Location: Scottish Borders
Hi Mazeroth,
I fear it might be even worse than DIY suggests.

If your average music level is -12db ref 0dbfs then the music stream is already using only the 14 least significant bits(LSB).
The two most significant bits (MSB) are set to zero and switch on briefly during music peaks which may only occur a few times in a recorded track.

If the average level drops to -13db you have now switched off the 3rdMSB as well although it will switch on quite regularly, if the recording is mastered to fully use the available bit range.

Now digitally decrease your volume before the DEQX and/or DCX and each -6db switch off the next MSB.
A cut of -12db would now effectively be only 12bits most of the time and -18db only 11bits.

Your average attenuated volume is now -30db below 0dbfs and produces a voltage of about 63mVac sent to your amp.

A gain of 34db here (1.25W into 8ohm) into 88db speakers gives 89db spl. This is still pretty loud to my ears and this is your average level at -12db with a further digital cut of -18db. Noise and distortion will by now be pretty obvious during many passages and particularly during quieter music.

Do try to avoid digital cut before your processor. OR convert everything to 20bit or better before exporting it from the PC. There's a challenge that with today's technology should be possible. Tell us of your success, I suspect a lot more than me are looking for a cheap solution to this.
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regards Andrew T.
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Old 11th February 2006, 05:03 PM   #4
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Join Date: May 2004
Location: Dallas, TX
Andrew,

Thanks for supporting my earlier post BTW: I think I've found the optimum soultion by using 3x Behringer A500 amplifiers. Most pro-amps have built in gain controls so you can drive them with a full rail-to-rail swing from your DCX. The A500 is fanless class AB and sounds great. The only problem with these amps is that they thump on powerup if you don't have the volumes turned all the way down...

--Chris
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Old 16th February 2006, 08:27 PM   #5
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Join Date: Jul 2004
Location: Columbus, OH
Thanks for the input.

Newbie...using the 3 Behringer amps how are you controlling the volume?
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Old 16th February 2006, 09:06 PM   #6
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Join Date: May 2004
Location: Dallas, TX
Mazeroth,

They each have built in gain controls. I have the levels set such that each amp's gain control is set to the same position and I just adjust all 6 at once..

Its not that bad since I usually set the volume once and leave it alone. The only time I need to change it is to increase it a bit when listening to LPs, but then I leave it alone for all my LP listening...

[EDIT] I should have mentioned, the gain controls are large knobs on the front of the amplifier, not hidden inside or on the back panel.

--Chris
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